The present invention relates to a rotary tablet press comprising a housing, a rotary die table having a number of dies arranged circumferentially, each die being associated with at least a first punch having a first end receivable in the die through an opening of the die and arranged for compression of a powder or granular material in the die by reciprocation of the punch, at least a cam for cooperation with a second end of the punches in order to effect axial displacement of the punches by rotation of the die table, a feeding device for the supply of material to be compressed into the dies, and a tablet discharge device for removal of compressed material in the form of tablets, wherein each die opening and its corresponding first punch end are enclosed in a compression chamber, said compression chamber comprising at least one dust extraction nozzle communicating with a dust extraction tube located outside the compression chamber.
US 2004/0207107 A1 (assigned to Courtoy N V) describes a rotary tablet press having dust extraction nozzles placed in appropriate positions in the compression chamber to prevent build-up of dust in the compression chamber. The suction system may advantageously be designed to constantly keep a certain under pressure in the compression chamber in order to prevent any leakage from the chamber.
Furthermore, it is well-known practice to provide the compression chamber of a rotary tablet press with a chimney-like, vertical air intake duct extending from an upper wall of the compression chamber to an intake opening at an area at the top of the rotary tablet press. Through this duct, air from the surroundings of the rotary tablet press may enter the compression chamber in order to replace air removed by means of dust extraction nozzles. The intake opening of the duct may be covered by means of a simple filter or a HEPA filter, if necessary. Such a filter may both ensure that the air entering the compression chamber is clean and that no powder or dust leaks from the compression chamber. However, such filters have the disadvantage that they become clogged during use, and therefore they must be monitored and replaced when necessary.
In another known application, the compression chamber is comprised by a compression unit detachably mounted in the housing of the rotary tablet press, and the compression unit is located in a compression section delimited by an upper partition wall and a lower partition wall of the housing of the rotary tablet press. A vertical air intake duct similar to the above explained projects from the upper side of the upper partition wall in order to enable air to enter the compression section from the surroundings of the tablet press. Thereby, air may by suction enter the compression chamber from the compression section through a hole in the wall of the compression chamber, or the compression chamber may be connected with the vertical air intake duct by means of a rigid or flexible pipe or tube connection extending through the compression section.